Seafood is a main source of human exposure to environmental pollutants, such as methyl mercury and lipophilic contaminants, including polychlorinated biphenyls (PCBs). In addition perfluorinated compounds (PFCs) biomagnify in ocean food chains, with the highest concentrations in marine mammals at high trophic levels. The investigators recently discovered that PFCs may adversely impact on human immune system development. Thus, in Faroese children, elevated PFC exposures were associated with reduced humoral immune response to routine childhood immunizations. The investigators now propose to extend this observation by utilizing existing and unique birth cohorts of Faroese and Greenlanders with high levels of seafood intake and traditional consumption of marine mammals high in ocean food chains. Due to the availability of extensive baseline data, follow-up examination of immune functions in the birth cohorts (250 subjects from each population) is feasible and will encompass outcomes at early school age through to young adult age in regard to exposures at different life stages, including intrauterine. As the main outcome, they will assess concentrations of specific antibodies in serum in response to childhood immunizations. The investigators will also determine the immune response in adults aged 28 to a booster dose (diphtheria and tetanus) and to vaccination with new antigens (hepatitis A and B). They will record the occurrence of allergic diseases and measure serum concentrations of total and specific IgE as possible immunotoxicity outcomes associated with prenatal and postnatal exposures. Advanced statistical models will be used to determine the relative contributions by PFCs and other ocean pollutants at different developmental stages and calculate benchmark dose levels for use in risk assessment. This new evidence will be of substantial importance for the understanding of immunotoxicity in humans with lifetime exposure to PFCs and other immunotoxic pollutants from marine food and for the risk assessment of these ocean pollutants.